Collection pages show groups of items, sometimes referred to as categories. In shopify a collection would be a category, you can create, edit and organize your collections from the main Shopify admin by entering:
Online store > Products > Collections
Within the theme there are also options on which content is shown and the order of that content.
How many products per page - Shopify has a limit of 50 products per page which must be respected.
The theme allows options to show 24, 36 or 48 products per page before pagination links to pages 2, 3, 4 will show at the bottom of a collection page.
How many products per row - Choose your layout to show 2, 3, 4, 5 or 6 products per row.
This will default to 2 products per row on mobile.
Show sort by - Allow customers to sort your products by name, date, price and best selling.
By default the collection pages will load in the order that you have specified within the collection admin.
Show sidebar - Adds a sidebar to your collection pages. when enabled you can add multiple menus or a list of vendors used within your products. The sidebar can also be set to stick to the side of the page in the instance that a short menu is used... For longer side menus the content will be deemed too tall to show all at once on some computers with a smaller height display.
Content - At the bottom of the collection page section content blocks can be added - within the Icon theme this will add menus to your collection page within a sidebar that will become active when a block of content has been selected. Add more menus to give easy navigation to your customers.